1. Field of the Invention
This invention generally relates to strings for producing musical tones and more particularly to the construction of improved wound musical strings and the method of making such strings.
2. Description of Related Art
When metal strings, typically steel strings, are placed in tension and struck or plucked, they vibrate and produce a musical tone. Some of these strings merely comprise a simple steel core wire, as used for treble notes in a piano. At lower frequencies, the string length increases. String lengths for the lowest notes become very long and cannot be incorporated in many pianos, such as spinet, upright and small grand pianos.
As known in the art, strings for the lower notes therefore incorporate a copper wrapping wire wound about a central portion of the core wire to load the wire and produce a tone with a string of significantly shorter length than would be required without the wrapping wire. Strings in the bass region may include one to three concentric windings. Each concentric winding has an intermediate section between two end turn sections.
U.S. Pat. No. 4,005,038 (1977) to Conklin, Jr. discloses an apparatus for wrapping strings for musical instruments that represents the conventional approach for producing such strings. The final wound string comprises a core wire of circular cross section. A single-, double- or triple-winding is coextensive with a central or intermediate length of the core wire. End turns of each winding wrap around a flattened area on the core wire produced by swaging or other similar technique. Winding the end turns around the swaged portion prevents the end turns from rotating on the core wire and loosening the entire wire wrap. Consequently in this form the core wire is circular except for the flattened transition areas that are coextensive with the end turns.
Many wound strings constructed in this conventional approach exhibit "false beats" when struck. It is generally recognized that one cause of false beats lies in the boundary conditions of orthogonal modes of vibration. More specifically such musical strings vibrate with components in various planes that shift around major axes displaced by 90.degree.. For example, in a horizontal string, the major axes are typically designated as the horizontal and vertical axes.
Tones emitted in the two orthogonal modes do not necessarily have identical speaking lengths. For example, in a piano it is quite possible for the pin that terminates the horizontal mode to be displaced from the corner of the bridge notching that terminates the vertical mode of vibration. Good bridge notching places the edge of the notch in line with the center line of the bridge pin to prevent false beats.
If the vibration components in both axes do not have identical frequencies, the difference represents a false beat. While the difference or false beat frequency may be minimal at the fundamental tone for the string, the frequency is multiplied by the partial number. Consequently at four octaves above the fundamental, the false beat frequency is sixteen times the beat frequency at the fundamental. Even if a string produces only a low slow frequency false beat in the low bass region, the overtones in the audible range beat much faster and thereby produce undesirable sounds. When objectionable false beats are detected, piano tuners generally replace the offending string in hopes that the problem will disappear because the effects from string to string tend to be random. The randomness comes from the possibility that the two ends can add or cancel depending on the orientation of the flats at each end.
Over the years a number of alternative string constructions have been proposed for a number of different purposes including the improvement of tonal quality. For example, U.S. Pat. No. 210,172 (1878) to Watson et al. and Great Britain Patent No. 300 (1885) to Hassel collectively disclose wound piano strings with core wires having triangular, oval, quadrangular, pentagonal or other polygonal cross sections. Both patents propose these cross sections to prevent loosening or longitudinal displacement of the wrapping wire on the core wire in a wound string.
U.S. Pat. No. 3,605,544 (1971) to Kondo discloses a string in which the end turns are wrapped in a contiguous fashion about a core wire. Intermediate turns, however, are spaced to eliminate undesirable resonances, buzzes or other noises, that is, to improve tonal quality.
U.S. Pat. No. 478,746 (1892) to Gill discloses another approach for improving tone quality. A string, whether wound or unwound, is formed with a triangular, rectangular or half-round cross section. In accordance with the Gill patent, however, any flat portion is located immediately above the corresponding note hammer so that the hammer strikes the flattened portion. This feature is stated to reduce hammer wear. In addition it is suggested that the string be twisted along its length to improve tone quality.
None of these references addresses the particular source of undesirable tone quality produced by false beats. Moreover none of the approaches suggested by these references seems to have been adopted in any wide-spread fashion. Pianos, particularly, continue to be manufactured with wound strings according to a method and construction as disclosed in the above-identified Conklin patent and other references. Moreover the cure for false beats when detected continues to be replacing the offending string.